By using a transmit beam forming (BF) or precoding technique and by using a receive signal combination technology, an multiple input multiple output (MIMO) wireless system can obtain diversity and array gains. A typical system that uses BF or precoding may usually be represented as:y=HVs+n 
where y is a received signal vector, H is a channel matrix, V is a precoding matrix, s is a transmitted symbol vector, and n is measured noise. Optimal precoding usually requires that a transmitter know entirely channel state information (CSI). In a common method, user equipment quantizes instantaneous CSI and feeds back the instantaneous CSI to a base station. CSI information fed back by an existing LTE R8 system includes an rank indicator (RI), a precoding matrix indicator (PMI), a channel quality indicator (CQI), and the like, where the RI and the PMI indicate respectively a quantity of used layers and a used precoding matrix. A set of used precoding matrices is generally referred to as a codebook (sometimes each precoding matrix in the set is referred to as a code word). An existing Long Term Evolution (LTE) R8 4-antenna codebook is designed based on Householder (Householder) transformation, and an R10 system further introduces double-codebook design for 8-antenna. The foregoing two codebooks are mainly for antenna design of a common base station. A common base station uses a fixed or remote electrical tilt downtilt to control a beam direction of an antenna in a vertical direction, and a beam direction of the antenna may be adjusted dynamically through precoding or beam forming only in a horizontal direction.
To reduce system costs and to achieve a higher system capacity and coverage requirement at the same time, an active antenna system (AAS) has been widely deployed in practice. For the currently launched LTE R12 standard, enhancement of communication performance after the AAS system is introduced is considered. Compared with a conventional base station antenna, the AAS further provides design flexibility in a vertical direction, and meanwhile, for convenience of deployment, antenna ports in the ASS may be further increased. For example, a quantity of antenna ports included in the current LTE R12 and future evolved versions may be 8, 16, 32, 64 or even larger. A new requirement for codebook design, especially in aspects such as precoding performance, feedback overhead compromise, and air interface support, is proposed. In such a background, a new design solution for an AAS base station antenna, and especially for a precoding matrix and a feedback process of the AAS base station antenna, needs to be proposed.